Commercial Kegs: Commercial beer kegs are available in four sizes: Half Barrel, Quarter Barrel, Slim Quarter Barrel and Sixth Barrel. These kegs are also referred to as a Full-Keg, Pony Keg (a shorter version of the full-keg, but same diameter), Slim Quarter and Torpedo Keg (43% narrower than a full-keg but the same height). The approximate full weight and number of drinks in each are as follows:                Half Barrel: 160 pounds/165.33-12 oz. drinks        Quarter Barrel/Slim Quarter: 90 pounds/82-12 oz. drinks        Sixth Barrel: 55 pounds/56-12 oz. drinks (60 cans of beer)        The majority of commercial beer kegs sold each year are half barrels. However, the sixth barrel keg is becoming the choice for many establishments, breweries and consumers that wish to use kegs smaller than a half barrel. The small footprint of a sixth barrel allows retailers to have a greater variety of beer in a small space. For the consumer, at approximately 34% the weight of a half-barrel, the sixth barrel provides a more convenient way to enjoy keg beer at home. In addition, consumers are finding more reasons to purchase sixth barrels given their smaller quantity of beer.        
The Influence of Craft Beers: The popularity of the sixth barrel kegs is growing in response to the growth of craft beers. Craft beer generally refers to beer that is brewed using traditional methods, without adjuncts such as rice or corn, and focuses on flavor, creativity and originality rather than mass appeal. In the past decade, craft beers have gained in popularity in the brewing industry. According to the American Brewers Association, total beer sales dropped 1.9% in 2013. However, craft beer sales grew 17.2%. In addition, craft beer's share of the total U.S. beer market in dollars grew to more than 14% in 2013, up from 10% in 2012.
Craft beers typically cost much more then mass-produced beers. In addition, studies have shown consumers drink less beer when drinking a craft versus a mass-produced beer due to the often higher alcohol content and fuller body of the craft beer. Due to these facts and its convenient size, establishments and consumers often purchase craft beer in the sixth barrel to avoid the costly impact of the beer going bad before it is consumed.
Craft beer breweries have responded by making the majority of craft beers available for purchase in the sixth barrel size. In addition, mass produced breweries are making their more popular brands available in the sixth barrel to compete with the crafts.
The convenient size and quantity of beer in the sixth barrel coupled with the craft beer trends are driving a change in the keg marketplace. Today, sixth barrels are more abundant than ever and are generally available at your local liquor store.
Home Brewing: According to the American Homebrewers Association, there are an estimated 1.2 million homebrewers in the United States. There are two primary methods for containing home brewed beer, bottles and kegs. The Cornelius keg is designed for the home brewer and is similar in size and shape to the sixth barrel. Storing homebrew in a keg is often preferred due to the ease of kegging beer rather than bottling.
Given the popularity and portability of the sixth barrel and Cornelius keg, it stands to reason that an ideal apparatus would be a portable container for storing, cooling and dispensing these types of kegs.